U.S. patent number 5,951,373 [Application Number 08/549,607] was granted by the patent office on 1999-09-14 for circumferentially oscillating carousel apparatus for sequentially processing substrates for polishing and cleaning.
This patent grant is currently assigned to Applied Materials, Inc.. Invention is credited to William R. Bartlett, Norm Shendon.
United States Patent |
5,951,373 |
Shendon , et al. |
September 14, 1999 |
Circumferentially oscillating carousel apparatus for sequentially
processing substrates for polishing and cleaning
Abstract
A polishing apparatus including a plurality of polishing pads on
respective rotating platens. The polishing platens, and therefore
the attached pads also, may be of substantially different
diameters. Multiple wafer heads can simultaneously polish multiple
wafers on the multiple polishing pads or at different positions on
one of the pads. The wafer heads are suspended from a rotatable
carousel, which provides positioning of the heads relative to the
polishing surfaces. Additionally, a loading/unloading station is
provided. The carousel selectively positions the heads on the
polishing surfaces, or positions one of the heads over the
loading/unloading station while the remaining heads are located
over polishing stations for substrate polishing, at which positions
the wafers can be polished. The carousel can rotate to sweep all
wafer heads attached thereto over respective polishing pads that
they overlie.
Inventors: |
Shendon; Norm (San Carlos,
CA), Bartlett; William R. (Los Gatos, CA) |
Assignee: |
Applied Materials, Inc. (Santa
Clara, CA)
|
Family
ID: |
24193705 |
Appl.
No.: |
08/549,607 |
Filed: |
October 27, 1995 |
Current U.S.
Class: |
451/41; 451/285;
451/289; 451/287 |
Current CPC
Class: |
B24B
37/32 (20130101) |
Current International
Class: |
B24B
37/04 (20060101); B24B 41/06 (20060101); B24B
007/00 () |
Field of
Search: |
;451/41,283,285,287,288,289,291,292,366 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Morgan; Eileen P.
Attorney, Agent or Firm: Fish & Richardson
Parent Case Text
RELATED APPLICATION
This application is related to concurrently filed and pending
application Ser. No. 08/541,336, filed Oct. 27, 1995, in the names
of Ilya Perlov, Eugene Gantvarg, Harry Lee, Norman Shendon, Sasson
Somekh, and Robert Tolles, entitled "Continuous Processing System
for Chemical Mechanical Polishing." This application is
incorporated herein by reference in its entirety.
Claims
What is claimed is:
1. An apparatus for polishing a substrate, comprising:
a first platen rotatable about a first axis and supporting a first
polishing surface having a first diameter;
a second platen rotatable about a second axis and supporting a
second polishing surface having a second diameter which is larger
than said first diameter,
a carousel including a first rotatable member rotatable about a
first point and a second rotatable member having a first end and a
second end, the second end of the second rotatable member suspended
from the first rotatable member;
a first wafer head assembly suspended from said first rotatable
member for holding a first wafer having a diameter smaller than the
first and second diameters;
a second wafer head assembly suspended from said first end of said
second rotatable member for holding a second wafer having a
diameter smaller than the first and second diameters;
a positioning member coupled to said carousel configured to rotate
said carousel and thereby position one of said wafer head
assemblies over any one of said polishing surfaces and to oscillate
at least one of said wafer head assemblies over one of said
polishing surfaces.
2. A polishing apparatus comprising:
a first rotatable platen and a second rotatable platen bearing
respective first and second polishing pads on upper surfaces
thereof, wherein said first platen has a first diameter
substantially larger than a second diameter of said second platen
and said first polishing pad is coarser than said second polishing
pad;
a carousel rotatable about a point; and
at least two wafer heads for holding respective wafers on bottom
surfaces thereof;
wherein said at least two wafer heads are held by said carousel at
respective points such that in a first rotational position of said
carousel said first and second wafer heads overlie said first
platen, and in a second rotation position of said carousel said
first and second wafer heads overlie different ones of said first
and second platens.
3. An apparatus for polishing a substrate, comprising:
a first platen supporting a first polishing surface having a first
diameter;
a second platen supporting a second polishing surface having a
second diameter which is larger than said first diameter;
a transfer station;
a carousel rotatable about an axis;
four wafer head assemblies suspended from said carousel at
approximately egual angular intervals, each wafer head assembly
holding a wafer having a diameter smaller than the first and second
diameters; and
a positioning member coupled to said carousel to rotate said
carousel and thereby position a first one of said wafer head
assemblies over said first polishing surface, second and third ones
of said wafer head assemblies over said second polishing surfaces,
and a fourth one of said wafer head assemblies over said transfer
station.
4. A polishing method, comprising the steps of:
providing a plurality of wafer heads on an assembly;
providing a plurality of polishing stations having different
polishing characteristics, each of said polishing stations
including a polishing surface having a diameter;
mounting wafers to said wafer heads, said wafers having diameters
smaller than the diameters of said polishing surfaces;
moving said wafer heads on said assembly so as to position first
and second ones of said wafer heads over the same polishing
surface;
moving said wafer heads on said assembly so as to position said
first one of said wafer heads over one of said polishing surfaces
and a second one of said wafer heads over another of said polishing
surfaces; and
unmounting said wafers from said first and second ones of said
wafer heads after said wafers have been processed by said polishing
stations.
5. An apparatus for polishing a substrate, comprising:
a first platen having a first diameter and supporting a first
polishing surface;
a second platen having a second diameter larger than said first
diameter and supporting a second polishing surface;
a carousel rotatable about an axis between a first position and a
second position;
a first wafer head assembly suspended from said carousel; and
a second wafer head assembly suspended from said carousel;
said first and second wafer head assemblies being held by said
carousel at locations such that in said first position said first
and second wafer head assemblies overlie said second polishing
surface, and in said second position said first wafer head assembly
overlies said first polishing surface and said second wafer head
assembly overlies said second polishing surface.
6. A polishing apparatus, comprising:
a plurality of rotatable platens for bearing respective polishing
pads on upper surfaces thereof;
a carousel, said carousel including a first member rotatable about
a first axis, and a second member supported by said first member
and rotatable about a second axis offset from said first axis;
and
at least two wafer heads for holding wafers on bottom surfaces
thereof, said two wafer heads including a first wafer head
suspended from said first rotatable member and a second wafer head
suspended from said second member.
7. The apparatus of claim 5, further comprising a positioning
member coupled to said carousel to rotate said carousel between
said first and second positions.
Description
FIELD OF THE INVENTION
The present invention in general relates to substrate polishing
apparatus, wherein the surface of a substrate is positioned against
a polishing surface such that relative motion between the substrate
surface being polished and the polishing surface causes the
substrate to be polished. In particular, the invention relates to a
substrate polishing apparatus in which a substrate is polished at
multiple polishing stations in a progressive polishing
sequence.
BACKGROUND OF THE INVENTION
Electronic integrated circuit devices are typically formed on
substrates, most commonly on semiconductor substrates, by the
sequential deposition and etching of conductive, semiconductive and
insulative film layers. As the deposition layers are sequentially
deposited and etched, the uppermost surface of the substrate, i.e.,
the exposed surface of the uppermost layer on the substrate,
becomes progressively more non-planar. This occurs because the
height of the uppermost film layer, i.e., the distance between the
outer surface of that layer and the surface of the underlying
substrate, is greatest in regions of the substrate where the least
etching has occurred, and least in regions where the greatest
etching has occurred.
This non-planar surface presents a problem for the integrated
circuit manufacturer. The etching step typically includes
depositing a photo-resist layer on the exposed surface of the
substrate, and then selectively removing portions of the resist bay
a photolithographic process to provide the etch pattern on the
layer. If the layer is non-planar, photolithographic techniques of
patterning the resist might not be suitable because the surface of
the substrate may be sufficiently non-planar to prevent focusing of
the photographic apparatus on the entire layer surface. Therefore,
a need exists to periodically planarize the substrate surface to
restore a planar layer surface for photolithography.
Polishing is also usable in a fabrication process in which a metal
layer is defined into metal lines with narrow spaces between. A
thick silicon oxide layer is then deposited to fill the spaces but
to also overfill so as to produce an oxide layer overlying the
metal lines, with a oxide layer having a generally planar top
surface. Polishing is then used to remove the silicon oxide down to
the metal lines and possibly remove a little more material
including both metal and oxide. As a result, this polishing is
effectively designed to be a planar process.
Chemical mechanical polishing is one accepted method of
planarization. This planarization method typically requires that
the substrate be mounted in a wafer polishing head with its surface
to be polished exposed at its surface facing the head. The head,
with the attached substrate, is placed against a rotating polishing
pad. The head may also rotate, to provide additional motion between
the substrate and the polishing surface. Further, a polishing
slurry is supplied to the interface between the pad and the
substrate being polished. This slurry typically includes an
abrasive and at least one chemically reactive agent therein, which
are selected to enhance the polishing of the film layers of the
substrate.
The polishing pad provides a surface having specified polishing
characteristics. Thus, for any material being polished, the pad and
slurry combination are theoretically capable of providing a
specified finish and flatness on the polished surface. Typically,
the actual polishing pad and slurry combination selected for a
given material are based on a trade off between the polishing rate,
and therefore the throughput of wafers through the machine, and the
need to provide a desired finish and flatness on the substrate on
the substrate. Because the flatness and surface finish of the film
layer can limit the utility of the substrate in subsequent
fabrication steps, the fabricator's selection of a polishing pad
and slurry are usually dictated by the needed finish and flatness,
and the polishing time is a resulting limitation on the throughput
of substrates through the polishing apparatus.
An additional limitation on polishing throughput arises because the
polishing material becomes packed with the debris of polishing, and
it also becomes compressed in the regions where the substrate was
pressed against it for polishing. This condition, commonly referred
to as "glazing", causes the polishing surface to become less
abrasive, with the result that the polishing time necessary to
polish any individual substrate increases. Therefore, the polishing
surface must be periodically restored, or conditioned, in order to
maintain a high throughput of substrates through the polishing
apparatus.
One method of increasing throughput uses a wafer head having a
plurality of substrate loading stations therein to simultaneously
load a plurality of substrates into the head in opposition to a
single polishing pad to enable simultaneous polishing of the
substrates on the single polishing pad. Although this method would
appear to provide substantial throughput increases over the
single-substrate style of polishing head, several factors militate
against the use of such carrier arrangements for planarizing
substrates, particularly after deposition layers have been formed
thereon. First, the head is complex, and, in order to attempt to
provide control of the loading of each of the substrates against
the pad, a substantial number of moving parts and pressure lines
must be provided. Additionally, the control over the polishing of
each of the substrates is limited, and is a compromise between
individual control and ease of controlling the general polishing
attributes of the multiple substrates. Finally, if any one
substrate develops a problem, such as if a substrate cracks, the
broken piece of the substrate may come loose and destroy all of the
substrates.
Therefore, the need exists in the art for a polishing apparatus
which enables the optimization of polishing throughput, flatness,
and finish while minimizing the risk of contamination or
destruction of any substrate.
SUMMARY OF THE INVENTION
The present invention provides a chemical mechanical polishing
apparatus and a method of using the apparatus that improves
throughput of substrates through the apparatus, and additionally
planarizes substrates with improved flatness and surface finish and
improved uniformity in the removal rate of material over the
surface of the substrate.
In one aspect of the invention, the apparatus includes multiple
polishing pads providing different polishing stages for polishing
the substrate. In particular, a first polishing pad may provide a
high material removal rate and a first finish and flatness on the
substrate, and a second or additional polishing pad provides a
finer finish and greater flatness on the substrate than possible
with the first pad. Alternative, the second polishing pad may
provide a different type of polishing, may provide similar
polishing in an in-line process, or provide a cleaning of the
substrate surface.
In each aspect of the invention, the substrates to be polished are
positioned at the relevant workstation, i.e., polishing surface or
cleaning station, by first loading the substrates into a wafer head
with the surface to be polished exposed, and then sequentially
positioning the substrate on the first polishing pad, the second
polishing pad, and then at the cleaning station. Multiple wafer
heads are linked to a carousel frame, which then moves the wafer
heads, and the substrates therein, from station to station.
The placement of the substrates on the workstations and the
duration of polishing or cleaning performed at each workstation are
preferably controlled by a controller, such as a microprocessor,
which is programmed to direct the positioning and loading of the
substrates to provide optimal polishing finish, flatness and
throughput.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of a polishing apparatus of the
present invention;
FIG. 2 is an end view of the polishing apparatus of FIG. 1;
FIG. 3 is a side sectional view of the apparatus of FIG. 1;
FIG. 4 is a partial perspective view of an alternative embodiment
of the apparatus of FIG. 1;
FIG. 5 is a partial view, partially in section, of the carousel
assembly including the two polishing heads of the apparatus of FIG.
1;
FIG. 6 is a sectional view of a polishing head of the apparatus of
FIG. 1;
FIG. 7 is a sectional view of the polishing head of FIG. 6, showing
the retainer extended from the polishing head;
FIGS. 8A and 8B are parts of a sectional view of the load/unload
apparatus of the polishing apparatus of FIG. 1;
FIG. 9 is a top view of the load/unload apparatus of FIGS. 8A and
8B;
FIGS. 10 through 16 are simplified cross-sectional view of the
load/unload apparatus of FIGS. 8A and 8B showing the loading and
unloading sequences;
FIGS. 17, 18, 19, and 20 are plan views showing the sequence of
processing steps using the polishing apparatus of FIG. 1;
FIG. 21 is a side cross-sectional view of a conditioning apparatus
usable with the invention;
FIG. 22 is a side cross-sectional view of the support structure for
the arm of the conditioning apparatus of FIG. 21;
FIG. 23 is a side cross-sectional view of the conditioning head of
the conditioning apparatus of FIG. 21;
FIG. 24 is a first alternative embodiment of the carousel of the
invention;
FIG. 25 is a plan view of the carousel of FIG. 24;
FIG. 26 is a second alternative embodiment of the carousel of the
invention;
FIG. 27 is a third alternative embodiment of the carousel of the
invention; and
FIG. 28 is a plan view of the carousel of FIG. 27.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
An Overview of the Apparatus
FIGS. 1 and 2 show a first embodiment of an integrated polishing
apparatus 100 of the invention which includes a plurality of
sub-systems therein useful for polishing and cleaning substrates to
provide a planarized substrate with minimal residual particulate
matter. In this embodiment of the invention, the sub-systems
include a first polishing station 200, a second polishing station
300, a loading and unloading station 400, and a substrate
positioning assembly 600. In use, individual substrates 10 are
loaded into individual wafer heads 602, 602' of the apparatus, and
are sequentially polished on the two polishing stations 200, 300.
After polishing, the substrates 10 are unloaded from the apparatus
100 at the loading and unloading station 400, and a new substrate
is placed into the wafer head 602 or 602'.
Preferably, the polishing apparatus 100 allows simultaneous
polishing by one of the heads and washing, loading or unloading of
substrates from the other of the heads at the loading and unloading
station 400. Additionally, each of the heads 602, 602' may be
positioned to polish the substrate therein on one or the other of
the polishing stations 200, 300 as shown in FIG. 1.
Assembly Structure
To support the various sub-systems of the invention, the polishing
apparatus 100 includes a machine base 102, over which an overhead
platform 104 is supported on a plurality of, preferably four, posts
106. The posts 106 provide fixed support and locating of the
overhead platform 104 relative to the machine base 102. The
overhead platform 104 is also preferably rotatable in the vertical
direction with respect to the machine base 102 by a hinge bar 108
extending between the ends of adjacent posts 106, and a hinge 100
hingedly connects the overhead platform 104 through that hinge bar
108 to the machine base 102. To secure the overhead platform 104
against movement about the hinge 110, securing members 114 extend
between the overhead platform 104 and the posts 106 and clamp them
together. Thus, during processing, the overhead platform 104 is
rigidly held on the posts 106, but when polishing is not being
performed the overhead platform 104 may be hinged upwardly at one
end thereof for servicing of the components of the polishing
apparatus 100, which would otherwise be blocked thereby.
The machine base 102 preferably includes an upper table 120, which
is supported by a frame, either a weldment, a casting, or a
plurality of, preferably six, legs 122. Each leg 122 provides
mechanical support of the table 120 to space the table from a
supporting surface, such as a floor. The table 120 preferably
includes a plurality of support rail members 123, which provide
support for the various sub-systems of the apparatus which are
housed in the machine base 102, and it also includes a table top
126 which protects the sub-systems mounted on the machine base 102
from liquids which may be flung off the polishing surfaces or
sprayed out of the loading/unloading station 400 during processing.
The table top 126 preferably includes four apertures therethrough
for providing access of the polishing stations 200, 300, the
loading/unloading station 400, and the conditioning apparatus 800
through the table top 126.
THE POLISHING STATIONS
FIGS. 1, 2 and 3 show the general structure of each of the
polishing stations 200, 300. The polishing stations 200, 300 are
substantially identical, except as specifically noted.
The First Polishing Station
The first polishing station 200 is located at an aperture 201 in
the table top 126 of the base 102, and supported thereon by a
plurality of bolts (not shown) or other fasteners secured to the
underside of the machine base 102. The first polishing station 200
includes a platen 202 which extends into the aperture and over
which a conformable polishing pad 204 is secured such as with a
removable adhesive. Preferably, materials such as Suba, IC-1000, or
IC-2000, all available from Rodel of Newark, Del., are used for the
pad 204. As shown in the cross section of FIG. 3, the platen 202
includes a planar, pad receiving surface 203,and is separated from
the table top 126 by a small annular gap 205. The platen 202 is
coupled, through a drive sheave 210 and a pulley or belt 206, to an
output sheave 207 of a drive motor 208. The drive motor 208 is
secured to the underside of the table top 126. The drive motor 208
provides sufficient torque to rotate the platen 202, and thus the
polishing pad 204, at a fixed rotational velocity as it
frictionally engages the wafer being processed. The pad 204
preferably is sized to be at least twice the diameter of the
substrate or larger.
An overhead slurry port 130 is rotatably supported on the table top
126 adjacent to the aperture 201 to direct a slurry to the exposed
surface of the pad 204. The slurry port 130 includes an adjustable
dispensing tube 132, such as bellows tubing, which terminates in an
orifice 134 overlying the pad 204. It is perhaps preferable that
the dispensing tube be mounted on the carousel 604 to be in fixed
relation with the wafer head 602 (or 602'). A slurry supply 136,
such as a pressurized source of slurry, is connected to the port
130 to provide slurry to the surface of the pad 204.
The Second Polishing Station
Referring still to FIGS. 1, 2 and 3, the second polishing station
300 preferably includes a second, smaller platen 302, having a
second polishing pad 304 thereon, which is rotated by a second
drive motor 306 secured to the horizontally extending beams 123.
Preferably, the output shaft of the second drive motor 306 is
directly coupled to the underside of the smaller platen 302. The
second motor 306 provides sufficient torque to drive the platen 302
at a constant velocity as it frictionally engages and polishes the
wafer. It is possible that a single motor drives both platens 202,
302.
The platen 302 preferably includes a planar surface 308 on which
the polishing pad 304 is received. The pad 304 is preferably sized
to be approximately one and one quarter to two times the diameter
of the substrate 10, although it may be larger, and to be
approximately the size of the platen 302. That is, the platen 302
of the second polishing station 300 is substantially smaller than
the platen 202 of the first polishing station 200. Exemplary
dimensions are 13 inches (33 cm) for the smaller platen 302 and 21
inches (53 cm) for the larger platen 202. However, many aspects of
the invention are applicable to multiple platens being of the same
size. The polishing station 300 is located immediately adjacent to
an aperture 320 in the table top 126, though which the platen 302
may be accessed.
As shown in FIG. 3, a dispensing port 330 located on the table top
126 adjacent to the aperture 320 directs a fluid such as slurry to
the exposed surface of the small pad 304. The dispensing port 330
includes an adjustable dispensing tube 332, such as bellows tubing,
which terminates in an orifice 334 overlying the pad 304. A fluid
supply 336, such as a pressurized source of water, is connected to
the dispensing port 330 to provide slurry or other fluid to the
surface of the pad 304.
The platens 202, 302 are each received within open basins 350,
through the lower termini of which the shaft of the sheave 205
extends to connect the first drive motor 208 to the first platen
202 and of which the motor drive shaft extends to connect the
second drive motor 306 and the second platen 302. These basins 350
also include a respective drain line 354 which drains to a sump.
The basins collect slurry, or liquids, which drain off of the pad
surface to be collected in a sump.
Referring now to FIG. 4, one alternative embodiment of the second
polishing station 200 invention is shown wherein the platen 302,
the basin 350 and the drive motor 306 are all mounted on a carriage
360 which is vertically movable with respect to the table top 126
of the apparatus. In the extended, or polishing, position, the
carriage 360 if the second polishing station 300 is located such
that the upper surface of the second platen 302 is located to be
substantially co-planar with the upper surface of first platen 202.
In a second position, as shown in FIG. 4, the carriage 360 is
retracted by hydraulic pistons 375 so that the platen 302 is
located approximately one to two inches (2.5 to 5 cm) below the
upper surface of the table top 126. In this position, a substrate
10 held in one of the wafer heads 602, 602' positioned over the
platen 302 may be sprayed by upwardly directed spray jets 361a
positioned near the end of a spray arm 361 inserted between the
table top 126 and the wafer head 602, 602', as is shown in FIG. 4,
to enable rinsing of the substrate 10 and the wafer head 602 or
602' over the platen 302 and the basin 350. By rinsing the
substrate 10 and the wafer head 602 or 602' (not shown in FIG. 4)
over the basin 350, the spent rinse water will collect in the basin
350 and be drained through the flexible drain line 354 to the sump.
Additionally, this configuration allows the substrate to be removed
from the wafer head 602, 602' at a station which does not also
include a cleaning or rinsing portion, thereby reducing the
required vertical stroke of the wafer head 602, 602'.
To provide the positioning of the components of the second
polishing station 300, the second drive motor 306 is supported by a
pair of rails 362, 364, which are mounted, through linear bearing
assemblies 366, 368, to a pair of opposed hangers 370, 372
suspended from the table top 126. Additionally, hydraulic pistons
375 link each of the rails 362, 364 to the table top 126, to
selectively position the carriage 360 of the second polishing
station 300 at the extended or the retracted position.
The Wafer Head Assembly
Referring to FIGS. 1 and 5 the preferred structure of the substrate
positioning assembly 600 is shown. This assembly preferably
includes a carousel 604, which is suspended from the overhead
platform 104, and the aforementioned wafer heads 602, 602' which
are suspended from the carousel 604 to selectively position
substrates 10 (not shown in these figures) received therein over
the polishing pads 204, 304 or over the loading/unloading station
400.
Referring now primarily to FIG. 5, the carousel 604 is rotationally
supported from the overhead platform 104 so as to allow positioning
of the wafer heads 602, 602' in a circular path across the table
top 126 and intersecting the polishing stations 200, 300 and the
loading/unloading station 400. This rotatable support is provided
by a circular sleeve 606, having an outwardly extending sleeve
flange 608 thereon, extending through an aperture provided therefor
in the overhead platform 104. A rotational bearing 610, such as a
roller bearing or a liquid film bearing having an annular profile,
is located between the upper surface of the overhead platform 104
and the lower surface of the sleeve flange 608. Thus, the sleeve
606 is rotationally suspended from the overhead platform 104. The
lower end of the sleeve 606 includes a carousel flange 612, which
is secured to the carousel 604 by a set of bolts 614.
To controllably rotate the carousel 604, a carousel drive motor 616
located on the overhead platform 104, as additionally illustrated
in perspective in FIG. 1, is coupled through a drive belt 618 to
the sleeve flange 608. The sleeve flange 608 has affixed to its
upper end a sleeve pulley 617 or sheave around which is wrapped the
belt 618, and the drive motor 616 includes a right-angled drive
coupling 620 on its output to drive a pulley 619 driving the belt
618. The drive motor 616 is preferably a stepper motor, which is
controlled by the system controller, to move the sleeve flange 608
through approximately 270 degrees of rotation in either a clockwise
or a counterclockwise direction, as will be further described
herein.
Referring now primarily to FIG. 5, the carousel 604 is preferably
configured as a right circular, hollow, utility cabinet within
which are enclosed pneumatic or hydraulic feed lines, electrical
cables and drive motors for rotating the heads 602, 602'. To
complete this cabinet configuration, the carousel includes a base
622, which extends horizontally in parallel to but vertically
offset from an upper plate 624, and side sheathing 625 which
extends vertically between the upper plate 624 and the base 622.
These elements define the boundaries of the cabinet. To provide the
rigid spacing between the base 622 and the upper plate 624, a
plurality of posts 626 (preferably four) are equally spaced about
the perimeter of the base 622 and the upper plate 624 inside the
sheathing 625, and the base 622 and upper plate 624 are secured to
the posts 626 by 614 bolts extending through the base, or upper
plate, and into threaded apertures (not shown) provided therefore
in the ends of the posts. To fix this cabinet assembly above the
polishing surface, the bolts 614 secure the upper surface of the
upper plate 624 to the carousel flange 612. Thus, as the drive
motor 616 rotates, the upper plate 624, and thus the entire
cabinet, will rotate in a corresponding direction about a vertical
axis. The sheathing 625 protects the utility connections and the
drive motors maintained in the cabinet.
FIG. 5 further shows the connections of the utilities to the heads
602, 602'. For ease of understanding, only the feeds required to
operate one of the wafer heads, specifically head 602, will be
discussed, it being understood that identical feeds are needed to
operate the other head 602'. Also, the number and type of feeds
depend upon the type and operation of the heads 602, 602', and
other head configurations may require different feeds. In the
illustrated embodiment of the invention, the feeds include four
fluid lines 626, 627, 628 and 629 for pneumatic pressure and for
water or other liquid. The lines 626 and 628 are coupled to
independent variable pressure sources. The fluid lines 627 and 629
are coupled to water supplies. To extend the fluid lines 626-629
into the carousel 604, the fluid lines 626-629 are routed along the
overhead platform 104, and then through the hollow interior portion
630 of the sleeve 606.
The fluid lines 626-629 are connected to the head 602 through
corresponding passages in a head drive shaft 642 extending
downwardly from the carousel 604, as will be farther described
herein, and a rotary union 644 is provided over the end of the
shaft 642 within the cabinet of the carousel 604. The rotary union
644 includes a cylindrical housing 648, which is sealed over the
shaft 642 with multiple seal rings (not shown) to enable the shaft
642 to rotate within the housing 648, but to create four annular
sealed chambers (not shown) which are laterally defined between the
inner surface of the housing 648 and the outer surface of the shaft
642 received therein and are vertically defined between pairs of
annular seal rings. A plurality of bores extend through the head
drive shaft 642, and each bore is connected by a side passage to
within one of the chambers.
A power cable 660 is required for each head 602, 602' being used.
Each terminates within the carousel 604 and is there connected to a
respective head drive motor 662. The head drive motor 662 is
preferably a variable speed DC motor, which is connected to a
horizontally rotating output pulley 664. Each head drive shaft 642
also includes an input pulley 666 thereon, and a drive belt 668
extends between the pulleys 664, 666 to enable the motor 662 to
drive the head drive shaft 642 in rotational motion.
To connect the wafer head 602 to the carousel 604, the head drive
shaft 642 preferably extends through a bearing retainer 670, which
extends through a pilot hole 672 in the base 622 of the carousel
604. Bearings 674 are located between at each end of the retainer
670 to retain the head drive shaft 642 therein, and to enable the
shaft 642 to rotate with respect to the carousel base 622 but
simultaneously support the head drive shaft 642 in the retainer
670. Preferably, the retainer 670 also includes an annular
outwardly extending flange 676 which is bolted to the underside of
the carousel bottom plate 622 about the perimeter of the pilot hole
672.
Referring now to FIG. 6, the internal structure of the wafer head
602 is shown in detail. This head is similar to one described by
Shendon in U.S. patent application, Ser. No. 08/488,921, filed Jun.
9, 1995. Preferably, the head 602 includes a bowl portion 680
having a downwardly facing recess 682 therein, and within which a
carrier plate 684 is received. To connect the head 602 to the head
drive shaft 642, the bowl portion 680 includes an upwardly
extending, externally threaded, boss 686 and the shaft 642
terminates against the raised boss 684. A cup-shaped perimeter nut
694, having a downwardly extending, internally threaded lip 696 and
a central recess 698 secure the head drive shaft 642 to the bowl
portion 680. The end of the shaft 642 extends through the recess
698, and a snap ring 690 is placed into a snap ring bore located
adjacent to the end of the shaft 642 after the shaft end is
extended through the bore 698. The snap ring 690 prevents
retraction of the shaft 642 from the bore 698. The cup-shaped
perimeter nut 694 is then locked over the boss 686 by threading the
lip 696 over the externally threaded surface of the boss 686,
thereby trapping the snap ring 690 between the cup-shaped perimeter
nut 694 and the bowl portion 680. To rotationally lock the head
drive shaft 642 and the bowl portion 680, the shaft 642 includes a
keyway 700 extending inwardly of its lower end, and the boss 686
also includes a keyway 702 which aligns with the shaft keyway 700
when the shaft 642 is received in the perimeter nut 694. A key
extends between the two keyways 700, 702. Alternatively, a pin may
be fit in two matching dowel holes 704 in the boss 686 and the
drive shaft 642.
The bowl portion 680 provides a substantially vertically fixed,
rotationally movable, reference surface from which the substrate 10
is loaded against the polishing surface. In the preferred
embodiment of the invention as shown in FIG. 16, the substrate
loading is accomplished by selectively positioning the carrier
plate 684 with respect to the reference surface provided by the
bowl portion 680 with a primary, upper loading assembly 710 and a
secondary, lower loading assembly 711. Preferably, the central
recess 682 is defined within the boundaries of the bowl portion
680, which in the preferred embodiment is a one-piece member,
having an upper, horizontally extending plate-like portion 714 and
a downwardly extending rim 716. The carrier plate 684 is received
within the recess 682 and is extendable therefrom to locate a
substrate received thereon against a polishing surface.
To enable selective positioning of the carrier plate 684 in the
recess 682, the primary loading assembly 710 includes a bellows 716
which extends between the underside of the upper plate 714 and the
upper surface of the carrier plate 684. This bellows 716 is sealed
at its connection to the carrier plate 684 and the upper plate 714
of the bowl member 680, and these connections are also of
sufficient strength to support the mass of the carrier plate 684
hanging from the body portion 680 without separation. Preferably, a
bellows cavity 721 is formed within a removable bellows insert 720,
which includes an upper bellows plate 722 and a lower bellows plate
724 between which the bellows 716 extend. The bellows 716 are
affixed to the plates 722, 724, to create the removable bellows
insert 720. To affix the bellows insert 720 to the body portion 680
and to the carrier plate 684, a plurality of unillustrated bolts
extend through the rim of the lower bellows plate 724 and into the
top of the carrier plate 684, and a plurality of unillustrated
bolts extend through the plate-like portion of the bowl portion 680
and into threaded holes in the upper bellows plate 722.
The secondary loading assembly 711 of the wafer head 602 includes a
bow chamber 730 which is formed within the carrier plate 684. The
bow chamber 730 is a sealable cavity having a thin, generally
planar flexible membrane 732 against which a conformable material
734, such as a piece of polishing pad material may be located to
form a conformable substrate receiving surface for the surface.
To polish a substrate using the head 602, a substrate is loaded
against the material 734 covering the planar surface of the
membrane 732. The head is then positioned over one of the polishing
pads 204, 304, and the bellows cavity 721 is pressurized to enlarge
itself to thereby bias the carrier plate 684 toward the polishing
surface and thereby load the substrate against the polishing
surface. To vary the pressure between the center and the edge of
the substrate, the bow chamber 730 is pneumatically pressurized.
Positive pressure will bend the flexible planar membrane 732
outwardly (downwardly), and the center of the planar surface will
extend furthest outwardly in a convex structure to increase the
loading between the substrate and the pad polishing surface near
the center of the substrate. Negative pneumatic pressure, on the
other hand, tends to create a concave structure.
Referring still to FIG. 6, the head 602 also preferably includes a
retainer ring 760, which, during polishing, extends into contact
with the polishing surface and which is otherwise retractable
inwardly and upwardly of the head 602. In the preferred embodiment
of the head 602, the retainer ring 760 is an annular member having
a planar base 764 on which a replaceable contact ring 766 is fixed,
and it further includes an outwardly extending annular ledge
portion 765. The bowl member 680 includes an inwardly extending
annular ledge 768, which extends below the surface of the outwardly
extending ledge portion 765 of the retainer ring 760. To secure the
retainer ring 760 within the recess 682 of the bowl member 680, a
plurality of compressed springs 770 extend between the inwardly
extending ledge 768 of the bowl member 680 and the underside of the
outwardly extending ledge 765 of the retainer ring 760. These
springs continuously bias the retainer ring 760 inwardly and
upwardly of the bowl member 680. To project the retainer ring 760
from the bowl member 680 and to vary and control the extent of
projection, a toroidal bladder 780, which is inflated through an
unillustrated tube stem, extends between the upper surface of the
outwardly extending ledge 764 of the retainer ring 760 and the
underside of a middle ledge 712 of the bowl member 680 about the
entire circumference of the retainer ring 760. When the bladder 780
is evacuated, as shown in FIG. 6, the retainer ring 760 is
retracted inwardly and upwardly of the head 602. When the bladder
780 is positively pressurized, as shown in FIG. 7, the bottom of
the retainer ring 760 extends downwardly from the wafer head 602.
The bladder 780 can be replaced by a pair of annular bellows joined
on respective ends to the middle ledge 712 of the bowl member 680
and the ledge 765 of the retainer ring 760.
Wafer Head Utilities Connections
The wafer head 602, as shown in FIG. 6, preferably includes a
plurality of bores extending vertically through the head drive
shaft 642 to connect utility sources to the wafer head components.
To vary the pressure in the bellows cavity 721, a bore 782 in the
drive shaft 642 connects to a passage 784 through the boss 686 and
the upper bellows cavity plate 722 into the bellows cavity 721. The
bore 782 through the drive shaft 642 is selectively pressurized
through the rotary union 644 by a variable pressure source (not
shown) which provides pressurized air to bias the carrier plate 684
toward the polishing surface, and also provides vacuum to retract
the carrier plate 684 into the bowl member 680. A bow chamber
passage 785 is connected from a bow chamber bore 752 in the drive
shaft 642 and into the bow chamber 730. The bow chamber bore 752 is
connected to a variable pressure source 802, which selectively
supplies pressurized air or vacuum to the bow chamber 730 to
increase or decrease the asymmetry of loading the substrate center
relative to loading the substrate edge. A bore 758 in the drive
shaft 624 is connected to a ring port 774 that is connected to the
stem of the toroidal bladder 780 When positive pressure is applied
to thereby expand the bladder 780, it moves the retainer ring 760
in the direction of the polishing surface to bias the carrier plate
684 toward the polishing surface and thereby frictionally engage
the wafer with the polishing pad. When negative pressure is applied
to contract the bladder 780, it retracts the retainer ring 760 and
thereby retracts the retainer ring 760 inwardly of the head.
Another bore 756 extending vertically through the drive shaft 642
communicates with a flush bore 778 extending through the bowl
member 680 to a plurality of flush ports 781 (only one is shown).
The bore 756 in the drive shaft 642 in turn communicates with a
source of deionized water through the rotary union. Deionized water
supplied through the flush bore 778 enables the head 602 to be
flushed rinsed with the deionized water. Finally, a vertical bore
788 in the drive shaft 642 communicates with a release bore 786
extending from the terminus of the shaft 642 into a plurality of
release ports 787 (only one is shown) adjacent to the recess 732
for the wafer. The vertical bore 788 communicates with a variable
pressure/water source 810. To secure the substrate to the membrane
734 of the head 602 during movement of the head between processing
stations, the release bore 786 is evacuated. To eject the substrate
from the head 602, pressurized water is flowed through the release
bore 786.
The Loading/Unloading Station
The details of the load/unload station 400 are shown in the split
cross-sectional view of FIGS. 8A and 8B and the plan view of FIG.
9. In the preferred implementation of the invention, the
load/unload station 400 manipulates substrates onto and off of the
substrate carrier plate 684 of the wafer heads 602, 602', and also
rinses the surfaces of the substrate and of the head 602, 602'. To
provide these features, the load/unload station 400 preferably
includes a generally circumferential outer basin shroud 402 located
above, and selectively positionable with respect to, the upper
surface of the table top 126 terminate. A plurality of gripping
finger assemblies 404 terminate within the shroud 402 and are
controllably arcuately positionable within the shroud 402. A spray
apparatus 406 located in the shroud 402 rinses the substrate and
the carrier plate 684. A substrate pedestal 408 is vertically
movable within the shroud. In use, one of the wafer heads 602, 602'
is located over the open end of the. shroud 402, and the shroud 402
is moved upwardly over the outer surface of the head 602, i.e.,
over the outer surface of the bowl member 680 of the head 602. As
the shroud 402 is moved upwardly, the head 602 is received within
the plurality of finger assemblies 404, at which time the substrate
10 and head 602 are sprayed with water emitted from the spray
apparatus 406 . The substrate is then ejected from the head 602,
and is supported on the substrate pedestal 408 and is centered
thereon by the finger assemblies 404, as will be described farther
herein. The shroud 402 then retracts to create clearance between
the load/unload station 400 and the head 602 so that the spray
apparatus 406 can rinse the back of the substrate and the empty
wafer head 602. The pedestal 408 then moves upwardly and positions
the substrate above the top of the shroud 402 where a robot blade
152 (shown in FIGS. 1 and 14) can access the substrate with a
vacuum chuck. The robot blade 152 then removes the substrate from
the pedestal 408, and places a new substrate thereon. The pedestal
408 moves up to receive the substrate, and then retracts into the
shroud to allow the blade to retract and the head 602 to be
positioned over the load/unload station 400. The pedestal 408 then
moves upwardly to press the substrate against the substrate
receiving surface of the head 602.
The Shroud
The shroud 402 is shaped like a cup with an overhanging inward lip
and provides a housing within which the remainder of the
load/unload station components are housed. It also provides a
shield to minimize spraying or splashing of water or rinsed slurry
and other polishing products from the load/unload station and onto
other apparatus components. The shroud 402 generally includes an
upper, bowl shaped portion 410, having an outer circumferential
wall 412, an inwardly extending upper lip 414 and a generally
circular base 415, and a hollow basin stem 416 extending downwardly
from an aperture 418 in the center of the base 415.
In the preferred embodiment of the invention, the upper end of the
basin stem 416 includes an outwardly extending flange 420, on which
the base 415 rests. A lower end 422 of the basin stem 416 includes
an inwardly extending flange 424 terminating in an aperture 425
through which a sleeve 426 vertically extends, and a plurality
(only one shown) of drain apertures 427 extending through the
flange 424. To retain the sleeve 426 on the stem 416, a cover nut
428 is threaded over a downwardly extending extension of the stem
416 adjacent the aperture 425. This nut 428 includes a plurality of
drain holes 429 (only one shown) therethrough, which register with
the drain apertures in the flange 424.
To position the shroud 402 relative to the table top 126, one end
of a pneumatic cylinder 430 is connected to the outer surface of
the basin stem 416 adjacent to the lower end thereof, and the
second end of the cylinder 430 is connected to the table top 126.
The cylinder 430 moves the shroud 402 upwardly and downwardly with
respect to the table top 126 and carries the pedestal 408 with
it.
The Finger Assemblies
Referring still to FIGS. 8A, 8B, and 9 but especially to FIG. 8A,
the Load/unload apparatus 400 includes a plurality of, preferably
three, finger assemblies 404. Each finger assembly 404 includes a
biasing portion 432 on the middle portion of the basin stem 416 and
a head gripping portion 434 in the shroud 402 within which a
substrate receiving portion 436 is located. The biasing portion 432
provides the alignment and positioning of the head gripping portion
434 to align the head 602 with bumpers 445 and to align the
substrate with the substrate aligning portion 436 at the distal
ends of fingers 447.
Referring to FIG. 8B, there are shown the details of one of the
biasing portions 432. Each of the three biasing portions are
preferably identical. The biasing portion 432 includes a pivot arm
437, having a lower pivot connection 438 fixed to the bottom of the
basin stem 416, an intermediate bias connection 439, and an
outwardly extending support arm 440 (FIG. 8A) on which the head
gripping portion 434 is received. The biasing portion 432 is
configured to swing about the pivot connection 438 to enable
movement of the gripping portion 434 to align the head 602 or
substrate 10.
In the preferred embodiment, a tubular sleeve 441 is received
within the stem 416, and the pivot connection 438 is connected to a
shaft 442 on the lower end of the tubular sleeve 441. The pivot arm
437 extends upwardly from the pivot connection 438 in the annular
space between the basin stem 416 and the tubular sleeve 441. The
upper end of the vertically extending pivot arm 437 terminates
above the upper surface of the base 415 of the shroud 402, and the
support arm 440 extends radially outwardly therefrom. To provide
the arcuate positioning of the pivot arm 437 about the shaft 442, a
biasing member 443, preferably an actuator, such as a double acting
pneumatic cylinder with a center rest position, has an output shaft
fixed connected to the swing arm approximately midway between the
pivot connection 438 and the upper terminus of the pivot arm 437.
The actuator 443 allows the pivot arm 437 to be swung in a small
arc about the pivot connection 438, but it tends to move the pivot
arm 437 to preselected positions to provide preselected locating of
the pivot arm 437, and thus of the radially extending support arm
440 and the finger assemblies 404 attached thereto. These positions
are the same for all three of the finger assemblies 434 so that
each of the finger assemblies 434 is spaced at a nearly identical
distance from the center of the substrate pedestal 408 for
concurrent operation of the three actuators 432.
Referring to the left side of FIG. 8A, each finger assembly 434
includes a finger base 444, on which are mounted two roller members
445 arranged generally circumferentially within the shroud 402, an
alignment pin 446 to restrict the rotation of the finger base 444,
and a pivot pin 456 about which the finger base 444 rotates.
Additionally, the radially innermost surface of the finger base 444
has a face chamfered on its upper side, which provides a tapered
substrate receiving face for badly misaligned wafers, as will be
discussed further herein. Each roller member 445 includes a central
pin 448 which extends upwardly from the base 444, and an outer
cylindrical body 449 supported over the pin on a pair of bearings
450, 450'. The body 449 of the bumper 445 also includes a
circumferential raised portion 451.
To secure the finger base 444 to the support arm 440, the pivot pin
456 extends upwardly from the support arm 440, and is received
within a pair of unillustrated bearings in a bore in the finger
base 444. Thereby, the finger base 444 may swing in a slight arc
about the pivot pin 456. This allows the body portion to swing
through a slight arc to accommodate slight misalignment between the
wafer head 602 and the load/unload apparatus 400 when the head 602
with attached substrate is first received in the shroud 402.
When the wafer head 602 is first received in the shroud 402, it may
be rotating. Therefore, the engagement of this rotating member with
the circumferential raised portion 451 of the rotatable bumper 445
will tend to cause the entire finger base 444 to swing arcuately
about the pivot pin 453. To prevent this, an alignment fork 454,
having an alignment slot between two tines, extends inwardly from
the circumferential face of the shroud 402, and a restraint pin 446
extends downwardly from the finger base 444 and into the alignment
slot. The slot allows radial movement of the finger body 444 in the
slot, but restrains against substantial circumferential motion of
the claw body 444.
Referring again to FIGS. 8A and 9, each finger assembly 434
includes two inner upwardly and outwardly tapered faces which are
located just outside of a circular locus at the diameter of a
substrate. The tapered faces of the three finger assemblies 434
therefore provide six substrate receiving surfaces, on which a
misaligned substrate may be deposited and readjusted during the
loading and unloading process.
The Substrate Support
Referring now to the central portion of FIG. 8A, the details of
construction of the substrate pedestal 408 are shown. Preferably,
the substrate pedestal 408 includes an upper, planar support face
460, which is positioned with respect to the shroud 402 by three
drive shafts 471 (FIG. 8B) connected to the bottom of a pedestal
stem 462 through three-legged spider 465 at the underside of the
pedestal 408. The pedestal stem 462 extends downwardly from the
underside of the pedestal 408 and through the sleeve 441 in the
basin stem 416 and then outwardly through the base of the basin
stem 416.
The pedestal stem 462 preferably includes a bore 464 extending the
axial length thereof, which intersects a plurality (only one shown)
of cross bores 465' within the support member 460. Spray heads 466
extend at one central location from the upper terminus of the bore
464 and at numerous offset locations from the cross bores 465' and
through the surface of the support face 460 to spray wash liquid in
a generally upward direction. At the lower end of the pedestal stem
462, the stem bore 464 terminates at the lift spider 465, which
includes a threaded aperture 468 therein which communicates with
the stem bore 464 for the pedestal spray heads 466. A water line is
received in the aperture 468, to provide water to the stem bore 464
and spray heads 466 at the top surface of the pedestal 408.
The lift spider 465 also includes a lift claw 470 extending
therefrom, which is connected to the rod 471 of a hydraulic piston
472 attached to a side of the basin stem 416 of the shroud 402.
When the piston 472 moves the rod 471, it vertically moves the
pedestal stem 462 relative to the basin stem 416, and thus moves
the substrate pedestal 408 upwardly or downwardly with respect to
the shroud 402.
As the pedestal 408 is moved upwardly and downwardly, it may pass
through the region of the fingers 447 of the finger assemblies 434
on which the substrate may be positioned because of misalignment.
To allow passage of the pedestal 408 past these fingers 447, six
recesses 473 (shown in FIG. 9) may extend into the edge of the
pedestal 460 at the locations of each of the fingers 447.
The Spray Apparatus
Referring now to the left side of FIG. 8A, the details of one spray
apparatus 406 are shown. In the preferred embodiment, three spray
apparatus are used, spaced 120.degree. apart about the perimeter of
the pedestal 408. Each spray apparatus 406 includes a tubular feed
member 480 which extends upwardly from a feed port 481 located
with, and adjacent to the base of the basin stem 416 to a position
adjacent to, and above, the bottom of the shroud 402. It further
includes a spray arm 484 extending from the upper terminus of the
feed member 480 and radially outwardly to a position adjacent the
inner surface of the circumferential wall of the shroud 402. An
upwardly extending spray housing 486 is formed at the outermost
position of the spray arm 484. The spray arm 484 includes a feed
passage 485 extending therethrough to communicate water, or other
fluids, from the tubular feed member 480 to a pair of spray nozzles
487, 487' which are located in the spray housing 486. One of the
nozzles 487 is positioned to direct a flow of water or other fluid
upwardly away from the pedestal 408 in the illustrated position,
and the second of the nozzles 487' is positioned to direct water,
or other liquid, downwardly in the direction toward the pedestal
408.
Operation ofthe Load/Unload Apparatus
The operation of the load/unload apparatus is shown sequentially in
FIGS. 8A, 9, 10 and 11. In FIG. 8A, the wafer head 602, with a
substrate 10 held on its bottom side, is located over the
load/unload station 400. When the wafer head 602, with a just
polished substrate 10, is positioned over the load/unload apparatus
400, the shroud 402 and the pedestal 408 are in the fully retracted
position.
Once the wafer head 602 is positioned in a centered position over
the load/unload station 400, the shroud 402 of the load/unload
station 400 is moved upwardly to the position shown in FIG. 10. As
the shroud 402 moves upwardly, the outer cylindrical face 681 of
the bowl member 680 of the head 602 is received within the area
surrounded by the rotatable bumpers 445 and is realigned by them as
required. The pneumatic actuators 443 are activated to push
inwardly the pivot arms 437 and hence the finger assemblies 434.
The bumpers 445 engage the sides of a misaligned head 602, and
together they realign it, after which finger assemblies 434 are
retracted outwardly and the carousel is locked in place. If the
head 602 is rotating, the bumpers 445 will also rotate. As the
entire unload assembly 400 moves up over the wafer head 602, and
the finger assemblies 434 engage the wafer head, one or more of the
pivot arms 437 may be pushed outwardly, and the double acting
pistons will restore the pivot arms 437, and thus the rotatable
bumpers 445, at the rest position which corresponds to alignment of
the substrate receiving portion of the head with the support
pedestal 408.
Once the wafer head 602 is properly positioned over the pedestal
408, the spray nozzles 487, 487' in the spray assemblies 406 and at
leasts the offset ones of the spray heads 466 in the substrate
pedestal 408 are supplied with clean, deionized water to spray the
just polished surface of the substrate 10 held in the wafer head
602 and the sides and other exposed surface of the wafer head 602
and the pedestal 408. Additionally, water may be flowed through the
flush passage 780 (FIG. 6) on the backside of the wafer head 602 to
clean the backside of the carrier plate 684, the exterior of the
bellows 716, and the exposed surfaces of the retainer ring assembly
760.
After the surfaces of the pedestal 408 are flushed with water, the
pedestal stem 462 and attached pedestal 408 are raised and the
bellows cavity of the wafer head 602 is pressurized, to position
the edge of a substrate 10 held on the substrate receiving surface
of the carrier plate 684 nearly on the pedestal 408. Then, as shown
in FIG. 11, the eject passages of the wafer head 602 are supplied
with water, under slight pressure, to eject the substrate 10 from
the wafer head 602 onto the pedestal 408. If the wafer head 602 has
remained badly misaligned, the wafer 10 falls onto the chamfered
upper faces of the fingers 447 of the finger assemblies 434 and
falls off them to be better centered. The bladder cavity is then
evacuated, to retract the carrier plate 684 into the wafer head
602.
The basin 402 and attached pedestal 408 are then retracted
downwardly away from the wafer head 602, as shown in FIG. 12. Then,
as shown in FIG. 13, the actuators 443 push inwardly the pivot arms
437 and attached finger assemblies 434 so as to align the wafer 10
on the pedestal. The finger assemblies 434 are then withdrawn
outwardly, as shown in FIG. 14.
To remove the substrate from the load/unload station 400, a robot
blade 152 is inserted between the bottom of the wafer head 602 and
the top of the shroud 402. The pedestal 408 is then raised above
the top of the shroud 402, as shown in FIG. 15, to place the wafer
10 directly below and substantially in contact with the robot blade
152. The robot blade 152 includes a plurality of vacuum apertures
on its lower face (not shown), which enable gripping of the
substrate to the blade 152. Once the substrate 10 contacts or
nearly contacts the robot blade 152, the vacuum apertures affix the
substrate to the blade 152, and the blade 152 retract from the
load/unload station 400 and deposits the substrate in a suitable
carrier (not shown).
To position a new substrate 10 on the wafer head 602, the robot
retrieves a substrate, and positions it over the load/unload
station 400. Before the robot 152 is positioned over the
load/unload station, the pedestal 408 is retracted slightly
inwardly of load/unload station 400. Once the blade 152 is
repositioned over the load/unload station 400, the pedestal 408 is
moved upwardly against the substrate (as in FIG. 15).
Once the new substrate 10 is received on the pedestal 408, the
robot blade 152 horizontally retracts from the region above the
pedestal 408 as the pedestal downwrdly retracts through the area
between the retracted finger assemblies 434 to a position 408'
shown by the dashed lines in FIG. 16 at which the tips of the
fingers of the finger assemblies 434 can engage the substrate 10.
The actuators 443 then move the pivot arms 437 and attached finger
assemblies 434 in an inward direction to align the substrate 10 in
a centered position on top of the pedestal 408 with respect to the
pedestal support member 408. The pedestal 408 is then raised to a
position above the top of the shroud 402. Then, the shroud 402 and
attached pedestal 408 are moved upwardly, as shown in the solid
lines of FIG. 16. The entire load/unload apparatus 400 then moves
upwardly, nearly to the position shown in FIG. 16, so that the
wafer 10 nearly abuts the bottom of the wafer head 602. The bellows
cavity of the wafer head 602 is then pressurized, to extend the
plate 684 into contact with the wafer 10. A vacuum is then pulled
through the vacuum passages in the head 602 to secure the substrate
to the plate 684, and the bellows cavity is evacuated to lift the
plate 684, and the substrate, inwardly into the wafer head, as
shown in FIG. 8A, to enable the wafer head 602 to be moved to the
polishing station 200 to begin substrate polishing.
The Preferred Polishing Sequence
Referring now to FIGS. 17 to 20, the passage of substrates through
the polishing apparatus is shown in sequence. Referring initially
to FIG. 17, the polishing apparatus 100 is shown as a first
substrate 10 is being loaded into the first wafer head 602 located
over the loading/unloading station 400. During the loading of the
first wafer head 602, the second wafer head 602' and a second wafer
10' held therein are located over the first polishing station
200.
The loading and unloading of substrates from the wafer head 602 is
contemplated to be a relatively fast operation such that the time
needed to load and unload is significantly less than the time which
the substrate 10 must be positioned against and preferably moved
over the polishing surface of the polishing pad 204 of the first
polishing station 200 during this one phase of the polishing of the
exposed surface of the first wafer 10. Once the first substrate 10
has been loaded into the first wafer head 602, the carousel 604 not
illustrated in FIG. 17 circumferentially oscillates in a reciprocal
about its center 604a to cause the first wafer head 602 and its
wafer 10 to reciprocally sweep through a predetermined arc to
polish the second wafer 10' held in the second wafer head 602' over
a first position 204a of the first polishing pad 204. Although its
motion is not illustrated, the second wafer head 602' also
circumferentially oscillates over the loading/unloading station
400; however, its lower face has been retracted vertically upwards
from the loading/unloading station 400, and it performs no
processing during the sweeping operation. The carousel 604 is
reciprocally rotated about the overhead platform 104 by rotating
the sleeve 606 with the carousel drive motor 616 through an arc of
approximately 10 to 20 degrees. During the loading of the substrate
onto the head 602 (or 602'), the carousel 604 should remain
stationary absent any specially designed load/unload station 400
which could move with the oscillating carousel 604. However, once
the substrate 10 is loaded into the head 602 (or 602'), the
sweeping action of the carousel 604 may continue.
Once the polishing endpoint is reached for the second wafer 10' at
the first polishing position 204a at the first polishing pad 204
(note that this endpoint refers only to the stage of polishing in
the preferred embodiment and not to the total polishing), the
carrier plate 684 in the second wafer head 602' is retracted, and,
as illustrated in the plan view of FIG. 18, the carousel 604
rotates about its center 604a, in a counterclockwise direction from
the perspective of FIG. 17, to position the second wafer head 602'
over the second polishing station 300 and simultaneously to
position the first wafer head 602 over a second polishing position
204b of the first polishing station 200. Once both heads 602, 602'
have been properly positioned, the vacuum conditions in the two
bladder chambers 718 of the two heads 602, 602' are vented, and the
chambers 714 are pressurized to urge the respective carrier plates
684, and thus the wafers 10, 10' thereon, into contact with the
polishing surfaces of the pads 204, 304 of the two polishing
stations 200, 300. Again, during polishing, the carousel 604 is
swept through an arc of typically approximately 10 to 20 degrees,
dependent on the diameters of the two polishing pads 204, 304 and
the proximity of the second polishing position 204b to the edge of
the first polishing pad 204. Note that FIG. 18 shows the first
wafer head 602 overhanging the edge of first polishing pad 204
while its attached wafer 10 remains at all times on the pad 204. It
is possible to cantilever a wafer over the edge of the polishing
pad, but such a cantilever position is not recommended. The large
sweep of the wafers 10, 10' over the two pads 204, 304 ensures that
the wafer heads 602, 602' pass the wafers 10, 10' over a
substantial radius ofthe polishing surfaces, and thereby use almost
all of the polishing surface for polishing, and thereby tend to
average out pad non-uniformities.
As described, the two wafers 10, 10' are simultaneously polished on
the two polishing pads 204, 304. The wafer polishing at the second
polishing station 300 is preferably performed with deionized water
rather than slurry, and is intended to clean the substrate of any
slurry embedded into the surface of the substrate during polishing
on the first polishing station 200, and to provide a finer surface
finish on the polished or planarized surface of the substrate. This
process is sometimes referred to as buffing. To provide the finer
surface finish, the second polishing pad 304 has a finer nap, which
will impart a smoother finish on the substrate.
Once the polishing of the substrate being polished on the second
polishing station 300 has reached a polishing endpoint, the
substrate can be removed from the apparatus so that the second head
602' may be used to polish an additional substrate. However,
typically in the joint and simultaneous polishing at the two
polishing stations 200, 300, the polishing time is controlled by
the initial rough polish at the first polishing station 200. At the
cessation of polishing at the second polishing station 300, the
bellows cavity 714 of the head 602' is evacuated, which lifts the
carrier plate 684 and the wafer 10' attached thereto off the
polishing pad 304 of the second polishing station 300. This lifting
is accomplished while the carousel continues to sweep the wafer
heads 602, 602' through the arc.
When the first stage of rough polishing of the first wafer 10 at
the second polishing position 204b on the first polishing pad 204
has reached its endpoint, the polishing is stopped by the carrier
plate 684 being retracted into the second head 602' so as to raise
the first wafer 10 above the polishing pad 204. Then, the carousel
604 again rotates, as illustrated in FIG. 19, to move the second
wafer head 602' and attached wafer 10' from a position over the
second polishing station 300 to a position above the
loading/unloading station 400. This carousel motion simultaneously
moves the first wafer head 602 from the second polishing position
204b to the first polishing position 204a of the first polishing
pad 204. Again, this motion is provided by rotating the carousel in
a counterclockwise direction from the perspective of FIGS. 18, 19
and 20.
When the second wafer head 602' is located over the
loading/unloading station 400, the polished wafer therein may be
rinsed and removed, and a new wafer placed in the second wafer head
602', as described in the proceeding description of the
loading/unloading station 400. Once a new, third wafer 10" has been
placed into the second wafer head 602', the carousel 604
reinitiates its circumferential oscillation so as to cause the
first wafer head 602 and attached wafer 10 to be reciprocally swept
across the first polishing position of the first polishing pad
204.
Once the polishing endpoint for rough polishing has been achieved
for the first wafer 10 located in the first wafer head 602 at the
first polishing position 204a of the first polishing station 200,
as illustrated in FIG. 20, the carousel 604 is rotated to place the
first wafer head 602 and attached first wafer 10 at the second
polishing station 300. and also to place the second wafer head 602'
with the attached third wafer 10 at the second polishing position
204b of the first polishing pad 204. Preferably, the positioning is
provided by moving the carousel 604 in a clockwise direction by
270.degree.. This backward rotation allows the carousel to rotate
no more than 360.degree. in its entire operation. Electrical and
fluid connections to the carousel 604 can be accommodated in this
limited rotation by flexible lines rather than substantially more
complex rotary unions and slip rings that would be required if the
carousel 604 were also rotated in the same direction between
successive positions. This 270.degree. motion swings the first
wafer head 602 over the loading/unloading station 400, to position
it over the second polishing station 300 and to place the second
wafer head 602' over the second polishing position 204b of the
first polishing pad 204. In this position, the carousel performs
its circumferential oscillation so as to rough polish the third
wafer 10" on the first polishing pad 204 and to fine polish the
first wafer 10 on the second polishing pad 304. This completes the
polishing of the first wafer 10, whereafter it is unloaded at the
loading/unloading station 400.
The process continues in the same fashion whereby one rough polish
of a wafer is performed simultaneously with a fine polish of
another wafer.
The process could obviously be improved by including at least two
more polishing heads 602' and 602'" so that two wafers are being
rough polished at the first and second polishing positions 204a and
204b of the first polishing station 200, while a third wafer at the
second polishing station 300 is being fine polished, a fourth head
being positioned over the loading/unloading station 400 while the
three-fold polishing is being performed.
The Conditioning Apparatus
Referring now to FIGS. 21, 22 and 23, there is shown the preferred
configuration of the conditioning apparatus 800 for use with the
polishing apparatus 100 of the present invention. The conditioning
apparatus 800 generally includes a loading and positioning member
802, a conditioning member 804 and a transfer arm 806, which
extends between the conditioning portion 804 and the loading and
positioning portion 802. To condition a polishing surface using the
conditioning apparatus 800, the loading and positioning member 802
rotates horizontally the transfer arm 806 to position the
conditioning member 804 suspended therefrom over the polishing
surface, and, once positioned over the polishing surface, provides
a downwardly directed force vector 808 at the end of the transfer
arm 806 to push the conditioning member 804 against the polishing
surface. The conditioning member 804 is also rotated in the
vertical direction to place the conditioning member 804 in
opposition to the polishing pad.
Referring now to FIG. 23, the preferred configuration of the
conditioning member 804 is shown in detail. The conditioning member
804 includes a conditioning plate 810, having a lower planar
conditioning surface 812, and a coupling 814 extending between the
plate 810 and the transfer arm 806. The coupling 814 transfers
rotary motion from a drive belt 818 and pulley 820 to the plate
810, but allows the plate to tilt about the axis of rotation 822 of
the pulley 820.
The coupling 814 includes a central shaft 824, a capture ring 826
and a bearing support ring 828 which provide the rotational
transfer and freedom of movement necessary for operation of the
conditioning plate 810. The shaft 824 includes a lower, annular,
spherical surface 830, an upper face 832 having a plurality of bolt
apertures 834 therein, and a bearing recess 836 extending partially
between the upper face 832 and the spherical surface 830. To
connect the pulley 820 to the shaft 824, a plurality of bolts 838
extend through apertures provided therefor through the pulley 820
and are received in the bolt apertures 834. To support the shaft
824 with respect to the transfer arm 806, the bearing support ring
828 extends through an aperture 840 in the transfer arm 806 and is
retained thereto by a plurality of bolts 842. The bearing support
ring 828, includes an inner circumferential face 844 and an upper,
inwardly extending rim 846, which define a bearing receiving recess
848. A pair of bearings 850, 850' are located within this bearing
receiving recess 848, and are spaced apart by an annular spacer
ring 856. To secure the bearings in the bearing receiving recess
848, an annular retainer 858 is placed over the lower end of the
bearing receiving recess 848, and a compressible spacer 860 is
located between the lowermost bearing 850' and the retainer 858.
The retainer 858 thus maintains the bearings 850, 850' within the
bearing receiving recess 848. The inner races of the bearings 850,
850' are received on the bearing recess 836 of the shaft 824. The
bearings allow the shaft 824 to rotate within bearing support ring
828, and thus within the transfer arm 806.
The capture ring 826 is used to capture the plate 810 on the shaft
824 while allowing sufficient vertical motion of the plate 810 with
respect to the shaft 824 to allow the planar face 812 of the plate
810 to tilt with respect to the shaft 824. Preferably, the capture
ring 826 includes a lower flange portion 860 which is connected to
the upper surface of the conditioning plate 810 with at plurality
of bolts, and an upwardly extending sleeve portion 864 having an
inwardly projecting capture rim 864 projecting from the hollow
interior thereof. The shaft 824 includes an outwardly projecting
capture flange 866, over which the capture rim 864 rides. During
normal polishing operations, the capture rim 864 does not contact
the capture flange 866. However, when the transfer arm 806 is used
to move the plate 810 on or off the polishing surface, the movement
of the capture flange 866 upwardly from the polishing surface
engages the capture flange 866 against the capture rim 864 to lift
the capture ring 826 and the plate 810 attached thereto off the
polishing surface.
To transfer rotational motion from the shaft 824 to the
conditioning plate 810, the conditioning plate 810 includes at
least one pin aperture 868 therein, in which a pin 880 is partially
received. The capture flange 866 includes a pin aperture 882
therein, having a diameter slightly larger than the outer diameter
of the pin 880. As the shaft 824 rotates, it swings the pin
aperture 882 and thus the pin 820 through a circular path, to
rotate the plate 810 about the axis of rotation 822.
To enable variable polar positioning of the plate 810 relative to
the shaft 824, the upper surface of the conditioning plate 810
further includes a central recess therein, within which is received
an insert 885 having a semi-spherical projecting surface 887. The
projecting surface 887 has a spherical radius equal to the distance
between the projecting surface 887 and the intersection of the
interface between the conditioning plate 810 and the polishing pad
204 with a centerline 884 of the plate conditioning 810.
Preferably, this semi-spherical projecting surface 887 is an
annular segment of a sphere, which is provided by a semi-spherical,
annular second insert 889 which is received within a recess
provided therefor at the center of the insert 885. A plurality of
caged balls 888 (only two shown) are located between the
semi-spherical projecting surface 887 and the spherical surface 830
on the lower end of the shaft 824. The balls form a bearing surface
which allows the plate to move relative to the shaft about a point
defined at the aforementioned intersection of the centerline 884
and of the base 812 of the plate 810 as the plate 810 encounters
high of low spots on the polishing surface. Thus, as the
conditioning plate 810 tilts, the base 812 of the plate 810 remains
substantially parallel to the upper surface of the polishing
surface, and thus one portion of the edge of the plate will not dig
into the surface of the polishing surface as high and low spots are
encountered by the conditioning plate 810. A compliant O-ring 889
is set in an annular recess between the insert 885 and the capture
flange 866 of the shaft 824 to provide increasingly strong
resistance to increasing tilt of the conditioning plate 810.
Preferably, the insert 885 includes a central bore 890 therein,
within which the head of a bolt 892 is received. The bore 890 also
includes an inwardly projecting annular lip, which traps the head
894 of the bolt 892 within the bore 890, and the shaft of the bolt
892 is threaded into a central threaded bore in the shaft 824. The
bolt 892 retains the insert 885 on the shaft 824. However, the head
of the bolt 892 is smaller than the bore 890 in the insert 885, and
therefore the insert may move substantially with respect to the
bolt 890 to allow the plate to tilt with high and low spots on the
polishing surface.
The Loading/Positioning Assembly
Referring now to FIG. 22, the details of the loading/positioning
assembly 802 are shown. The loading/positioning assembly 802
generally includes a mount 910, which is received on the apparatus
cover and provides a grounded reference surface, a transfer arm
positioning assembly 912 and a shaft rotation assembly 914. The
transfer arm 806 is received on the loading/positioning assembly
802 to enable positioning of the conditioning member 810 on the
polishing surface and biasing of the conditioning member 810
against the polishing surface.
The mount 910 is a hollow cylindrical sleeve having a lower annular
mounting flange 920 at its lower terminus, a contoured outer
cylindrical face 822 extending upwardly from the mounting flange
920, and an upper inwardly extending bearing flange 924. The mount
910 is received over a conditioning arm aperture 928 in the
apparatus table top 120, and it includes a downwardly extending
pilot portion, which forms an inner guide which is securely sleeved
into the upper terminus of the conditioning aperture 928. This
ensures secure positioning of the mount 910 on the table top 120.
The mounting flange 920 also includes a plurality of pilot holes
930 (only one shown) therethrough, through which bolts (not shown)
extend into apertures (not shown) provided therefore in the table
top 120 to secure the flange 920 to the table top 120.
The interior cylindrical surface of the mount 910 includes a lower,
inwardly facing circumferential face 932, an upper, inwardly facing
circumferential face 934, and a pair of annular recesses 936, 938.
These annular recesses include first and second inverted annular
mounting surfaces 940, 942 from which the transfer arm positioning
assembly 912 and the shaft rotation assembly 914 are suspended.
The transfer arm positioning assembly 912 generally includes a
drive apparatus 944 which is coupled to a drive system 946 which
terminates in a rotary coupling 948 rotatably connected to proximal
end of the transfer arm 806. In the preferred embodiment, the drive
apparatus 944 includes a drive motor 950, having a gear 952 output,
which is suspended from a hanger 954 attached to the first inverted
annular mounting surface 940. The hanger 954 is preferably
connected to the first inverted annular mounting surface 940
through an extension sleeve 955 which is bolted to the first
inverted annular mounting surface 940. The gear 952 is meshed with
flywheel gear 956 located on a harmonic drive 958, which is
coupled, through a support web structure 960, to a transfer shaft
962.
The support web structure 960 and the transfer shaft 962, a bearing
support sleeve 964 is received over the outer surface of the
transfer shaft 962, and this sleeve 964 includes an upper bearing
pilot 965, a lower bearing pilot 966 and an outwardly extending
mounting flange 968. The mounting flange 968 is received within the
annular recess 936, and is secured on the second inverted annular
mounting surface 942. The support web structure 960 includes a
lower annular bearing recess 972 adjacent the perimeter of the
connection of the support web structure 960 and the shaft 962, and
the shaft 962 includes a shaft bearing recess 974 located adjacent
to the upper terminus of the sleeve 964. An upper roller bearing
978 extends between the shaft bearing recess 974 of the shaft 962
and the upper bearing pilot 965 of the sleeve 964, and a lower
roller bearing 976 extends between the annular bearing recess 972
of the web structure and the lower bearing pilot 966 of the sleeve
964. The bearings 976, 978 provide radial stability to the shaft
942 as the shaft is rotated and as the conditioning plate 810 is
loaded against the polishing pad 204.
To transfer rotational motion of the transfer shaft 962 to the
transfer arm 806, the shaft 962 includes a annular transfer rim 980
extending radially outwards from its middle. A transfer arm cover
plate 982 is received over the transfer rim 980, and is secured
thereto by a bolt 984 which extends through a hole 986 in the
transfer arm cover plate 982 into a threaded aperture in the
transfer rim 980 which is located through the flange at a position
on the transfer rim 980 which is directly opposite the nominal
position of the conditioning plate 810 on the polishing surface.
Additionally, to align the transfer arm cover plate 982 on the
transfer rim 980, a plurality of pins 986 extend from the cover
plate 982 and into clearance bores 988 in the transfer rim 982. The
cover plate 980 also includes a pivot flange 990 extending
therefrom, over which a yoke 992 of a pneumatic piston housing 994
is received. A pneumatic piston rod 996 extends upwardly from the
piston housing 994 and is rotatably coupled to the transfer arm
806. By varying the extension of the piston rod 996 from the
housing 994, the bias or load of the conditioning member 804 on the
polishing surface can be varied. Additionally, by fully retracting
the rod 996 into the housing 994, the conditioning member 804 may
be lifted from the polishing surface.
Preferably, the transfer arm cover plate 982 rotates the transfer
arm 806 and the conditioning member 804 over the entire
circumference of the transfer rim 980. When the conditioning member
804 is pressed on the polishing surface, the center of inertia of
the transfer arm 806 is maintained substantially co-linearly with
the center of rotation of the transfer shaft 962.
By operating the drive motor 950, the gear 952 horizontally rotates
the transfer shaft 962 through the torque-increasing harmonic drive
958 and thereby moves the conditioning plate 810 of conditioning
member 802 through an arc centered on the center of rotation of the
transfer shaft 962. The motor can be moved through a path along an
arc sufficient to sweep the conditioning plate 810 across the
polishing surface, and then reversed, to move the conditioning
surface through a reverse path along the arc. Thus, the
conditioning plate 810 may be repeatedly swept back and forth along
the surface of the polishing surface to condition the pad.
Additionally, when the conditioning member 804 is removed from the
polishing surface, the motor 950 is operated to sweep the
conditioning member 804 to the side of the polishing surface.
Referring still to FIG. 22, the shaft rotation assembly 914 rotates
the conditioning member 804 in a horizontal plane in juxtaposition
to the polishing pad 204. Preferably, the rotation assembly 914
includes a conditioning plate drive motor 1000 which is held by the
hanger 954, and a conditioning plate drive shaft 1002 which is
coupled to the conditioning plate drive motor through gears and
which extends upwardly through a bore through the middle of the
support web structure 960 and the transfer shaft 962 wherein it
terminates above the transfer shaft 962 in a horizontally rotating
pulley 1004. Importantly for the self-tensioning, the pulley 1004
is positioned above the rotary coupling 948. The drive belt 818
extends between the pulley 1004 and the sheave 820 about the
conditioner head to transfer rotational output of the conditioning
plate drive motor 1000 to the conditioning plate 810.
As the conditioning plate 810 is positioned on the polishing
surface and rotated with respect thereto, the lower, i.e.,
conditioning, surface 812 of the plate will encounter glazed and
unglazed regions of the polishing surface. The structure of the
conditioning apparatus 800 uniquely provides inherent variable
loading of the conditioning plate lower surface 812 against the
polishing surface in response to changes in the polishing surface
condition, which are manifested as changes in coefficient of
friction at the interface between the plate lower surface 812 and
the polishing surface interface. Specifically, as the conditioning
plate 810 rotates on the polishing surface of the pad 204, a
coefficient of friction is present at the interface of the plate
lower surface 812 and the polishing surface. As glazed portions of
the polishing surface are encountered by the plate 810, the
coefficient of friction at the interface decreases. This decrease
in coefficient of friction reduces the torque needed to drive the
plate 810 at a constant velocity, causing the tension in the belt
818 to decrease. This decrease in tension is transferred, as a
reduced force vector, at the coupling of the belt 818 to the drive
pulley 1004. Because this force vector is transferred to the
conditioning plate drive shaft 1002 at a distance equal to the
displacement to the pulley 1004, the force vector change creates a
moment on the end of the shaft 1002 tending to increase the load of
the conditioning plate 810 against the polishing surface. Likewise,
when the plate 810 moves from glazed to unglazed portions of the
conditioning surface, the coefficient of friction between the plate
810 and the polishing surface increases, increasing the tension on
the belt and thereby creating a moment on the drive shaft 1002
tending to decrease the loading of the plate 810 against the
polishing surface.
The Alternative Carousel Configuration
In the above-described embodiment of the apparatus, the carousel
provides a hard connection between the two wafer heads 602, 602',
i.e., the two heads 602. 602' may not be moved relative to one
another. However, process efficiency would be increased if the
wafer head 602 (or 602') is continuously swept in an arc on the
polishing surface 204 or 304 even during loading and unloading of
the other wafer head. However, where the wafer heads 602 and 602'
are rigidly interconnected, substrate loading and unloading from
and to a moving head becomes problematic. Either a very complex
loading and unloading apparatus must be provided to move with the
wafer head 602 (or 602') being loaded or unloaded as the wafer head
602' (or 602) polishes a different substrate and sweeps it in the
arcuate path across the polishing surface 204, or the wafer heads
must remain stationary during the load and unload cycle. Therefore,
as will be further described herein, the carousel may be configured
to maintain one of the wafer heads stationary over the load/unload
station 400 while allowing the other head to be arcuately swept on
the polishing surface 204 or 304. The same mechanisms can be
extended to first do a short, fine polish at polishing station 300
and then unload the wafer from the same wafer head 602 while the
second wafer head 602' continues a rough polish at polishing
station 200.
Referring to FIGS. 24 through 28, there are shown three different
alternative embodiments of the carousel which will provide
stationary positioning of one of the heads while the other of the
heads is swept over the polishing surface 204.
Referring first to FIGS. 24 and 25, the first alternative carousel
1100 includes the carousel plate 624, from which a plurality of
hanging posts 1104 suspend a lower, slotted, plate 1102. The wafer
head 602 is fixedly suspended from the lower, slotted plate 1102 as
in the previously described embodiment of the carousel. However,
the wafer head 602' is independently suspended from a slide plate
1106, on which the second head drive motor 1108 and second head
drive coupling 1110 are also mounted. The wafer head drive shaft
1112 for the head 602', which extends downwardly from the slide
plate 1102, extends through an arcuate slot 1114 in the slide plate
1102. By moving the drive shaft 1112 along the slot 1114, the wafer
head 602' may be swept through an arc as the wafer head 602 remains
stationary for loading and unloading of substrates.
To provide the sweeping motion, the sweep plate 1106 includes an
arcuate segment 1116 from which the wafer head 602' is suspended,
an alignment bore 1118 which is positionable at the center of the
lower plate 1102, and a partial annular geared ring 1120 which
extends from opposite sides of the arcuate segment 1116 and
generally above, and coextensive with, the outer circumference of
the lower plate 1102. A segment shaft 1126 extends upwardly from
the center of lower plate 1102, and is there received within the
alignment bore 1118. A sweep bearing 1128 connects the segment
shaft 1126 to the arcuate segment 1116 at the alignment bore 1118
to enable rotation of the segment 1116 about the segment shaft
1126.
To support the segment 1116 and the ring 1120, a bearing 1129
extends circumferentially at the radius of the ring 1120 between
the ring 1120 and segment 1116 and the lower plate 1104. The
bearing supports the mass of the sweep plate 1106 and the wafer
head drive components (i.e., the second head drive motor 1108 and
second head drive coupling 1110) on the lower plate 1102 while
allowing relative movement therebetween. To provide this movement,
a segment drive motor 1130 is suspended from the carousel plate
624, and the output shaft thereof includes a pinion gear 1132 which
is meshed to the geared ring 1120. By rotating the pinion gear
1132, the geared ring 1120 is moved arcuately, thereby moving the
ring 1120, and the segment 1106, in a circular path about the
segment shaft 1126. The motor 1130 rotates the pinion gear 1132 in
one direction, and then reverses the direction, to sweep the wafer
head 602' back and forth in an arcuate path as the carousel
otherwise remains stationary to allow a substrate to be removed
from, and loaded into, the wafer head 602.
Referring now to FIG. 26, there is shown a second alternative
embodiment of the carousel. This alternative carousel 1200 includes
a modified lower plate 1202 through which a secondary drive shaft
1204 into engagement with a secondary lower plate 1206, and a
secondary drive system 1208 for sweeping the secondary lower plate
1206 through a defined arc.
The modified lower plate 1202 includes a central clearance aperture
1210 therethrough, through which the secondary drive shaft housing
1204 loosely extends, and an arcuate slot 1212 through which the a
wafer head drive shaft housing 1214 loosely extends. The drive
shaft housing 1214 encloses a drive shaft 1215. A secondary lower
plate 1206 includes a wafer head drive shaft aperture 1216 through
which the polishing head drive shaft housing 1214 extends and an
arcuate slot 1218 through which another drive shaft housing 1220
extends. The drive shaft housing 1214 is fixed to the underside of
the secondary lower plate 1206. The other drive shaft housing 1220
encloses a drive shaft 1221 for rotating the wafer head 602. The
modified lower plate 1202 is connected to the lower end of the
secondary drive shaft 1204, which is rotated, by the secondary
drive system 1208, to rotate the modified lower plate 1206 through
an arc equal to the arcuate length of the slots 1212, 1218.
To support the modified lower plate 1202, a support sleeve 1230,
having a bearing recess 1232 therein, extends downwardly from the
perimeter of the modified lower plate 1206. A roller bearing 1234,
which extends about the circumference of the bearing recess 1232,
is received in the recess 1232. The inner race of the bearing 1234
rides in this recess. The bearing 1234 enables relative rotational
motion between the two plates 1202 and 1204.
Referring now to FIGS. 27 and 28, a third alternative construction
for positioning the wafer heads 602, 602' is shown. In this
embodiment, the carousel is eliminated, and the wafer heads 602,
602' are coupled to hanger apparatus 1300 which extends downwardly
from the overhead platform 104. Preferably, the hanger apparatus
1300 includes a support sleeve 1302 extending downwardly from the
overhead platform 104. The sleeve 1302 includes an upper bearing
bore 1304 and a lower bearing bore 1306 located at the ends of the
sleeve 1302. A first, hollow, drive shaft 1310 is supported within
the support sleeve 1302 on bearings 1312, 1314 which are received
in the bearing bores 1304, 1306. The lower end of the sleeve 1302
supports an outwardly extending support segment 1318, which is a
planar segment of steel plate, having a bore 1320 extending
therethrough. A wafer head support sleeve 1322, through which the
wafer head drive shaft 1324, is supported on bearings, extends
through the bore 1320, and is secured to the segment 1318. A drive
motor 1326 is supported on the support segment 1318 to rotate the
drive shaft 1324 to thereby rotate the wafer head 602.
An inner drive shaft 1330 extends through the first hollow drive
shaft 1310, and is supported therein on bearings 1332, 1334. The
ends of the inner shaft 1330 extend beyond the ends of the outer
shaft 1310. At the lower end of the inner shaft 1330, a second
outwardly extending support segment 1340, which is a planar segment
of steel plate, having an offset bore 1342 extending therethrough,
is received. The second outwardly extending support segment 1340
positions the second wafer head 602' by positioning the support
sleeve therefor through the bore 1342 and supporting a second drive
motor 1344 thereon. The upper ends of the shafts 1310, 1330 are
preferably coupled to separate drive motors (not shown), such as by
belts, pulleys, gears or direct shafting. These motors provide the
positioning of the wafer heads 602, 602' at the polishing stations
200, 300 and at the load/unload station 400.
Although the system has been described in terms of polishing
semiconductor wafers, the term wafer can be used in the larger
sense of any workpiece having a planar surface on at least one side
thereof that requires polishing. Indeed, the workpiece need not be
substantially circular as long as the wafer head is adapted to
received a non-circular workpiece.
Although the invention has been described in terms of an integrated
polishing apparatus, each of the subsystems may be used
independently of the other sub-systems to provide their intended
function
The invention thus provides an integrated polishing system capable
of high throughput of polished wafers. The polishing may be
accomplished by a multistage process including multiple grades of
polishing as well as washing.
* * * * *